The first thing I do with a water feature, whether it's a little tabletop bowl or a tiered stone thing, is turn it on and just listen. That sound is the entire point. Too tinny and splashy and it'll grate on you by week two. A proper low burble, something with a bit of depth to it, is what you want sitting under a window or near the patio chairs. If it sounds like a dripping tap, walk away.
Where it goes matters more than people expect. Keep it away from anything delicate and leafy that hates getting constantly misted, and away from furniture cushions or cheap outdoor rugs that will hold damp and start to smell. Wood decking right under the splash zone is a mistake too, it will darken and warp faster than you think. Give it a spot on stone, gravel, or a hard patio surface, somewhere water can land without causing a slow, quiet problem you won't notice until the wood's gone soft underfoot.
If you've never owned one, start small and simple. A self contained tabletop or pedestal fountain with its own reservoir and pump is the easiest way in, no plumbing, no pond liner, just fill it with water and plug it in. Go for one with real weight to it, stone or thick resin rather than anything that feels hollow and light when you lift it, because a lightweight one will walk itself across a patio in a decent wind and that's a mess nobody wants to clean up. The heavier, sturdier ones also tend to run quieter, which matters more than the pretty details once it's actually in place.
For sizing, measure the actual spot first, not the space you imagine it in. A tiered feature that looks modest in a shop photo can dominate a small patio once you see it next to your chairs. Stand where you'll usually be sitting and picture the thing at eye level or lower, since most feel wrong looming over a seating area. For a balcony or small courtyard, tabletop or small pedestal size is almost always the right call. For a proper garden, you can go bigger, but check the weight too, because some of the larger stone ones need two people and a dolly, not a cheerful afternoon of good intentions.
The one mistake to avoid is buying on looks alone and skipping the sound test, because you will be living with that noise every single day you're out there, and a feature that looks beautiful but sounds wrong is one you'll end up turning off and forgetting about within a month.